/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.jndi;

import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

import javax.naming.Context;
import javax.naming.NamingException;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;

import org.springframework.aop.framework.ProxyFactory;
import org.springframework.beans.SimpleTypeConverter;
import org.springframework.beans.TypeConverter;
import org.springframework.beans.TypeMismatchException;
import org.springframework.beans.factory.BeanClassLoaderAware;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.config.ConfigurableBeanFactory;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;

/**
 * {@link org.springframework.beans.factory.FactoryBean} that looks up a
 * JNDI object. Exposes the object found in JNDI for bean references,
 * e.g. for data access object's "dataSource" property in case of a
 * {@link javax.sql.DataSource}.
 *
 * <p>The typical usage will be to register this as singleton factory
 * (e.g. for a certain JNDI-bound DataSource) in an application context,
 * and give bean references to application services that need it.
 *
 * <p>The default behavior is to look up the JNDI object on startup and cache it.
 * This can be customized through the "lookupOnStartup" and "cache" properties,
 * using a {@link JndiObjectTargetSource} underneath. Note that you need to specify
 * a "proxyInterface" in such a scenario, since the actual JNDI object type is not
 * known in advance.
 *
 * <p>Of course, bean classes in a Spring environment may lookup e.g. a DataSource
 * from JNDI themselves. This class simply enables central configuration of the
 * JNDI name, and easy switching to non-JNDI alternatives. The latter is
 * particularly convenient for test setups, reuse in standalone clients, etc.
 *
 * <p>Note that switching to e.g. DriverManagerDataSource is just a matter of
 * configuration: Simply replace the definition of this FactoryBean with a
 * {@link org.springframework.jdbc.datasource.DriverManagerDataSource} definition!
 *
 * @author Juergen Hoeller
 * @see #setProxyInterface
 * @see #setLookupOnStartup
 * @see #setCache
 * @see JndiObjectTargetSource
 * @since 22.05.2003
 */
public class JndiObjectFactoryBean extends JndiObjectLocator
        implements FactoryBean<Object>, BeanFactoryAware, BeanClassLoaderAware {

    @Nullable
    private Class<?>[] proxyInterfaces;

    private boolean lookupOnStartup = true;

    private boolean cache = true;

    private boolean exposeAccessContext = false;

    @Nullable
    private Object defaultObject;

    @Nullable
    private ConfigurableBeanFactory beanFactory;

    @Nullable
    private ClassLoader beanClassLoader = ClassUtils.getDefaultClassLoader();

    @Nullable
    private Object jndiObject;


    /**
     * Specify the proxy interface to use for the JNDI object.
     * <p>Typically used in conjunction with "lookupOnStartup"=false and/or "cache"=false.
     * Needs to be specified because the actual JNDI object type is not known
     * in advance in case of a lazy lookup.
     *
     * @see #setProxyInterfaces
     * @see #setLookupOnStartup
     * @see #setCache
     */
    public void setProxyInterface(Class<?> proxyInterface) {
        this.proxyInterfaces = new Class<?>[] {proxyInterface};
    }

    /**
     * Specify multiple proxy interfaces to use for the JNDI object.
     * <p>Typically used in conjunction with "lookupOnStartup"=false and/or "cache"=false.
     * Note that proxy interfaces will be autodetected from a specified "expectedType",
     * if necessary.
     *
     * @see #setExpectedType
     * @see #setLookupOnStartup
     * @see #setCache
     */
    public void setProxyInterfaces(Class<?>... proxyInterfaces) {
        this.proxyInterfaces = proxyInterfaces;
    }

    /**
     * Set whether to look up the JNDI object on startup. Default is "true".
     * <p>Can be turned off to allow for late availability of the JNDI object.
     * In this case, the JNDI object will be fetched on first access.
     * <p>For a lazy lookup, a proxy interface needs to be specified.
     *
     * @see #setProxyInterface
     * @see #setCache
     */
    public void setLookupOnStartup(boolean lookupOnStartup) {
        this.lookupOnStartup = lookupOnStartup;
    }

    /**
     * Set whether to cache the JNDI object once it has been located.
     * Default is "true".
     * <p>Can be turned off to allow for hot redeployment of JNDI objects.
     * In this case, the JNDI object will be fetched for each invocation.
     * <p>For hot redeployment, a proxy interface needs to be specified.
     *
     * @see #setProxyInterface
     * @see #setLookupOnStartup
     */
    public void setCache(boolean cache) {
        this.cache = cache;
    }

    /**
     * Set whether to expose the JNDI environment context for all access to the target
     * object, i.e. for all method invocations on the exposed object reference.
     * <p>Default is "false", i.e. to only expose the JNDI context for object lookup.
     * Switch this flag to "true" in order to expose the JNDI environment (including
     * the authorization context) for each method invocation, as needed by WebLogic
     * for JNDI-obtained factories (e.g. JDBC DataSource, JMS ConnectionFactory)
     * with authorization requirements.
     */
    public void setExposeAccessContext(boolean exposeAccessContext) {
        this.exposeAccessContext = exposeAccessContext;
    }

    /**
     * Specify a default object to fall back to if the JNDI lookup fails.
     * Default is none.
     * <p>This can be an arbitrary bean reference or literal value.
     * It is typically used for literal values in scenarios where the JNDI environment
     * might define specific config settings but those are not required to be present.
     * <p>Note: This is only supported for lookup on startup.
     * If specified together with {@link #setExpectedType}, the specified value
     * needs to be either of that type or convertible to it.
     *
     * @see #setLookupOnStartup
     * @see ConfigurableBeanFactory#getTypeConverter()
     * @see SimpleTypeConverter
     */
    public void setDefaultObject(Object defaultObject) {
        this.defaultObject = defaultObject;
    }

    @Override
    public void setBeanFactory(BeanFactory beanFactory) {
        if (beanFactory instanceof ConfigurableBeanFactory) {
            // Just optional - for getting a specifically configured TypeConverter if needed.
            // We'll simply fall back to a SimpleTypeConverter if no specific one available.
            this.beanFactory = (ConfigurableBeanFactory) beanFactory;
        }
    }

    @Override
    public void setBeanClassLoader(ClassLoader classLoader) {
        this.beanClassLoader = classLoader;
    }


    /**
     * Look up the JNDI object and store it.
     */
    @Override
    public void afterPropertiesSet() throws IllegalArgumentException, NamingException {
        super.afterPropertiesSet();

        if (this.proxyInterfaces != null || !this.lookupOnStartup || !this.cache || this.exposeAccessContext) {
            // We need to create a proxy for this...
            if (this.defaultObject != null) {
                throw new IllegalArgumentException(
                        "'defaultObject' is not supported in combination with 'proxyInterface'");
            }
            // We need a proxy and a JndiObjectTargetSource.
            this.jndiObject = JndiObjectProxyFactory.createJndiObjectProxy(this);
        } else {
            if (this.defaultObject != null && getExpectedType() != null &&
                    !getExpectedType().isInstance(this.defaultObject)) {
                TypeConverter converter = (this.beanFactory != null ?
                                           this.beanFactory.getTypeConverter() : new SimpleTypeConverter());
                try {
                    this.defaultObject = converter.convertIfNecessary(this.defaultObject, getExpectedType());
                } catch (TypeMismatchException ex) {
                    throw new IllegalArgumentException("Default object [" + this.defaultObject + "] of type [" +
                            this.defaultObject.getClass().getName() + "] is not of expected type [" +
                            getExpectedType().getName() + "] and cannot be converted either", ex);
                }
            }
            // Locate specified JNDI object.
            this.jndiObject = lookupWithFallback();
        }
    }

    /**
     * Lookup variant that returns the specified "defaultObject"
     * (if any) in case of lookup failure.
     *
     * @return the located object, or the "defaultObject" as fallback
     * @throws NamingException in case of lookup failure without fallback
     * @see #setDefaultObject
     */
    protected Object lookupWithFallback() throws NamingException {
        ClassLoader originalClassLoader = ClassUtils.overrideThreadContextClassLoader(this.beanClassLoader);
        try {
            return lookup();
        } catch (TypeMismatchNamingException ex) {
            // Always let TypeMismatchNamingException through -
            // we don't want to fall back to the defaultObject in this case.
            throw ex;
        } catch (NamingException ex) {
            if (this.defaultObject != null) {
                if (logger.isDebugEnabled()) {
                    logger.debug("JNDI lookup failed - returning specified default object instead", ex);
                } else if (logger.isInfoEnabled()) {
                    logger.info("JNDI lookup failed - returning specified default object instead: " + ex);
                }
                return this.defaultObject;
            }
            throw ex;
        } finally {
            if (originalClassLoader != null) {
                Thread.currentThread().setContextClassLoader(originalClassLoader);
            }
        }
    }


    /**
     * Return the singleton JNDI object.
     */
    @Override
    @Nullable
    public Object getObject() {
        return this.jndiObject;
    }

    @Override
    public Class<?> getObjectType() {
        if (this.proxyInterfaces != null) {
            if (this.proxyInterfaces.length == 1) {
                return this.proxyInterfaces[0];
            } else if (this.proxyInterfaces.length > 1) {
                return createCompositeInterface(this.proxyInterfaces);
            }
        }
        if (this.jndiObject != null) {
            return this.jndiObject.getClass();
        } else {
            return getExpectedType();
        }
    }

    @Override
    public boolean isSingleton() {
        return true;
    }


    /**
     * Create a composite interface Class for the given interfaces,
     * implementing the given interfaces in one single Class.
     * <p>The default implementation builds a JDK proxy class for the
     * given interfaces.
     *
     * @param interfaces the interfaces to merge
     * @return the merged interface as Class
     * @see java.lang.reflect.Proxy#getProxyClass
     */
    protected Class<?> createCompositeInterface(Class<?>[] interfaces) {
        return ClassUtils.createCompositeInterface(interfaces, this.beanClassLoader);
    }


    /**
     * Inner class to just introduce an AOP dependency when actually creating a proxy.
     */
    private static class JndiObjectProxyFactory {

        private static Object createJndiObjectProxy(JndiObjectFactoryBean jof) throws NamingException {
            // Create a JndiObjectTargetSource that mirrors the JndiObjectFactoryBean's configuration.
            JndiObjectTargetSource targetSource = new JndiObjectTargetSource();
            targetSource.setJndiTemplate(jof.getJndiTemplate());
            String jndiName = jof.getJndiName();
            Assert.state(jndiName != null, "No JNDI name specified");
            targetSource.setJndiName(jndiName);
            targetSource.setExpectedType(jof.getExpectedType());
            targetSource.setResourceRef(jof.isResourceRef());
            targetSource.setLookupOnStartup(jof.lookupOnStartup);
            targetSource.setCache(jof.cache);
            targetSource.afterPropertiesSet();

            // Create a proxy with JndiObjectFactoryBean's proxy interface and the JndiObjectTargetSource.
            ProxyFactory proxyFactory = new ProxyFactory();
            if (jof.proxyInterfaces != null) {
                proxyFactory.setInterfaces(jof.proxyInterfaces);
            } else {
                Class<?> targetClass = targetSource.getTargetClass();
                if (targetClass == null) {
                    throw new IllegalStateException(
                            "Cannot deactivate 'lookupOnStartup' without specifying a 'proxyInterface' or "
                                    + "'expectedType'");
                }
                Class<?>[] ifcs = ClassUtils.getAllInterfacesForClass(targetClass, jof.beanClassLoader);
                for (Class<?> ifc : ifcs) {
                    if (Modifier.isPublic(ifc.getModifiers())) {
                        proxyFactory.addInterface(ifc);
                    }
                }
            }
            if (jof.exposeAccessContext) {
                proxyFactory.addAdvice(new JndiContextExposingInterceptor(jof.getJndiTemplate()));
            }
            proxyFactory.setTargetSource(targetSource);
            return proxyFactory.getProxy(jof.beanClassLoader);
        }
    }


    /**
     * Interceptor that exposes the JNDI context for all method invocations,
     * according to JndiObjectFactoryBean's "exposeAccessContext" flag.
     */
    private static class JndiContextExposingInterceptor implements MethodInterceptor {

        private final JndiTemplate jndiTemplate;

        public JndiContextExposingInterceptor(JndiTemplate jndiTemplate) {
            this.jndiTemplate = jndiTemplate;
        }

        @Override
        public Object invoke(MethodInvocation invocation) throws Throwable {
            Context ctx = (isEligible(invocation.getMethod()) ? this.jndiTemplate.getContext() : null);
            try {
                return invocation.proceed();
            } finally {
                this.jndiTemplate.releaseContext(ctx);
            }
        }

        protected boolean isEligible(Method method) {
            return (Object.class != method.getDeclaringClass());
        }
    }

}
